The original gamma camera systems used one detector head. Originally, the one detector head was positioned above an organ to be imaged. Subsequently, the one detector head was used for what is known as single photon emission computerized tomography (SPECT) or emission computerized tomography (ECT). SPECT or ECT involve mounting the camera detector head in a gantry enabling it to rotate or orbit about the patient so as to obtain tomographic data and thereby provide tomographic images. Another aspect in the development of the gamma cameras is whole body imaging wherein the gamma camera head is passed over the entire body to obtain a complete image of the patient.
To increase the efficiency of the whole body scans and the tomographic scans, multi-headed cameras have been used. First, dual-headed cameras were used wherein the gamma camera system comprised a pair of camera heads spaced apart and oppositely disposed to enable obtaining images from opposite sides of the patient simultaneously. For example, the dual heads were moved around the patient with one head on each side of the patient.
Recently triple-headed gamma camera systems have been used. In triple-headed gamma camera systems, the heads are mounted to form a triangular shape with the three planes of the heads each separated by 60.degree..
It would seem that multi-headed cameras would reduce the rotational travel required to obtain imaging data from a 180.degree. orbit or a 360.degree. orbit. It is true that with two oppositely disposed heads, the 360.degree. orbital data can be obtained with a 180.degree. rotation. However, the 180.degree. orbital data cannot be obtained in a scan of 90.degree.. Similarly, with a three-headed camera system, a 360.degree. scan can be accomplished with an orbital movement of a little over 120.degree.. The 180.degree. orbital data, however, also requires a scan of 120.degree.. From scan travel distances required it is seen that the 360.degree. scan times are drastically reduced by multi-head systems. However, when 180.degree. scans are required such as for cardiac studies, there is little or no time saving when using multi-headed cameras. Accordingly, a more efficient camera system is required for cardiac studies.
Another problem with the presently available gamma camera systems is in obtaining images during cardiac exercise studies. In these studies a static image is acquired while the patient pedals on an ergometer, for example. If a single camera head is used for data acquisition during the exercise study, it is oriented in an optimal left anterior oblique position. However, the behavior of the inferior wall of the heart which is of great interest to cardiologists cannot be seen from this orientation. Accordingly, a camera system is required wherein the image of the heart during exercise also includes a good view of the inferior wall of the heart.
Thus, what the present cameras do not provide is a two-headed gamma camera system with the heads oriented relative to each other to enable cardiac ECT studies in a reduced scan time. The arrangement of the two heads in the gamma camera system should assure that there is no minimum radius of rotation. The three-headed systems presently available inherently have a minimum radius of rotation which interferes with some studies, such as in pediatric applications.
Also presently lacking are gamma camera systems that can efficiently image during exercise studies and obtain images of the heart including the inferior wall. The gamma camera system that overcome the above noted deficiencies should also provide increased count rates to enhance first pass studies.